Studies On Phylogenetic Relationship And Molecular Mechanism Underlying Echolocation And Hibernation In Bats By Transcriptomics Analysis

Bats, belonging to the order Chiroptera, are one of the largest groups in mammals, which in total has more than 1100 bat species. Living bats were traditionally divided into suborders Megachiroptera and Microchiroptera based on morphological traits. Megabats have good dim light vision and do not have laryngeal echolocation, and they take fruits or nectar as food. However, microbats are generally smaller than megabats. They have poor vision and most sophisticated laryngeal echolocation ability, and they take insects as food. However, recently molecular evidence divided bats into two new suborders Yinpterochiroptera and Yangochiroptera. Now, this two classification have been reported by related studies. In fact, bats have long been regarded as special animals. Except for echolocation, they also have truly powered flight capacity and hibernation ability. These phenotype traits help bats adapt to envirenoment very well. Therefore, studies on the molecular and genetics basis underlying these traits are very meaningful for biological research in bats. In this dissertation, we mainly studied the phylogenetic relationship of bats, and molecular mechanism underlying the echolocation and hibernation based on transcriptome data generated by next-generation sequencing technology.The first part of dissertation is the study on the phylogenetic relationship of bats. Phylogenomic analysis has been proved to be a powerful approach to resolve the evolutionary relationship of organisms. In this study, we totally generated twelve bat brain transcriptome dataset by deep sequencing and preformed phylogenomic analysis to resolve the interrelationship of bats. Next, combined with published mammalian genome sequences, we generated the phylogenetic tree. Our result robustly supported for the’Yinpterochiroptera-Yangochiroptera’ classification of bats, which fully supported previous studies.The second part of dissertation is the study on the molecular mechanism underlying echolocation in bats. Gene expression variation was regarded as essential means to generate biological diversity. Inner ear, as an important hearing organ, their morphological structure and physiological are different between echolocating and non-echolocating bats. In this work, we studied the molecular mechanism underlying echolocation by comparing inner ear transcriptome between Myotis ricketti (echolocating bat) and Cynopterus sphinx (non-echolocating bat). We found that up-regulated genes in the Myotis ricketti involved in biological process such as ’cochlea morphogenesis’,’inner ear morphogenesis’and’sensory perception of sound’.The third part of dissertation is the study on the molecular mechanism underlying hibernation in bats. We studied the genetic basis of bat brain during the hibernation on the gene expression level. We found 1573 significant differentially genes by comparing summer active and winter torpid brain transcriptome of Rhinolophus ferrumequinum (greater horseshoe bat). Interestingly, in the torpid brain, these genes might involve in the biological process such as’metabolic suppression’,’cellular stress responses’and’oxidative stress’. Moreover, these biological process were also regarded as physiological basis of in the bat brain during hibernation.In a word, we made a tentative study on the phylogenetic relationship of bats, molecular mechanism underlying echolocation and hibernation of bats on omics level. In addition, our work provided valuable resource for comparative genomics and function genes studies in bats.